AOPA Turbine Pilot Magazine - April 2019 - T-12

unstable approaches the pilots continue the
approach to landing instead of performing
the go-around. What's more, pilots are 30
times more likely to press on in the face of an
unstabilized approach than go around. And
since they are far more likely to get away with
it than suffer an excursion, each landing leads
to a normalization of the belief that an unstable approach can end successfully.
These poorly flown approaches are most
likely to lead to excursions when flown to
wet, slush- or snow-covered, or otherwise
slippery runways. And it doesn't help that
the industry has found it is exceedingly difficult to predict exactly how much runway
will be needed to stop an airplane when
conditions are other than dry. The Boeing
study found that in more than half of nondry runway excursions, the runway was wet
only-that is, not contaminated by standing
water or frozen precipitation. Yet in 75 percent of these wet-only accidents, the braking
action experiences were more consistent
with snow-or even ice-than with accepted
models of stopping on wet runways.
The FAA echoed this alarming fact with
the publication of Safety Alert for Operators
15009, "Turbojet Braking Performance on
Wet Runways." It states that "several recent
runway landing incidents/accidents have
raised concerns with wet runway stopping
performance assumptions. Analysis of the
stopping data from these incidents/accidents indicates the braking coefficient of
friction in each case was significantly lower
than expected for a wet runway."
There are similar difficulties predicting
braking performance on snow. In an attempt
to refine performance planning during winter conditions, some Canadian airports
report a Canadian Runway Friction Index
(CRFI) value for snow- or ice-covered runways. This is a vehicle-measured coefficient
of maximum braking available that the pilot
can use to adjust their dry landing distance
calculations to an expected required distance based on the contamination present.
Somewhat depressingly, one of the most
commonly experienced contaminants-
a thin layer of dry snow-experiences the
largest range in braking degradation. An aircraft normally stopping in a total distance of
2,400 feet could, when landing on a mere 3
mm of dry snow, require from 4,000 feet to
as much as 6,300 feet to come to a stop. And
without a recent measurement a pilot has no
idea where in the range their performance
right now will fall.
T-12 | AOPA PILOT April 2019

SPOTLIGHT ON OVERRUNS

The NTSB final reports on noncommercial fixed-wing turbine aircraft overruns
reveal a common thread of touching down past the proper touchdown point, with
improper braking and excessive speed also playing a role in several accidents.
September 27, 2015: Cessna 550, Sarasota Bradenton International Airport
(SRQ) in Florida.
Probable cause: The pilot's failure to attain the proper touchdown point and to
adequately slow the airplane within the available runway, which resulted in a
runway overrun.
August 21, 2015: Eclipse EA500 at Danbury Municipal Airport (DXR) in
Connecticut.
Probable cause: The pilot's failure to attain the proper touchdown point.
March 1, 2015: Bombardier Canadair CL600-2A12, Marco Island Executive
Airport (MKY) in Florida.
Probable cause: The failure of a spring inside the number 2 brake's upper brake
control valve and the fracture of the coupling subassembly of the number 1 wheel
speed sensor during landing, which resulted in the loss of braking action, and the
pilot in command's deactivation of the antiskid system even though there were
no antiskid failure annunciations, which resulted in the rupture of the numbers 1, 3,
and 4 tires; further loss of braking action; and subsequent landing overrun.
November 21, 2014: Embraer 500, Sugarland Regional Airport (SGR) in Texas.
Probable cause: The pilot's engagement of the emergency parking brake during
the landing roll, which decreased the airplane's braking performance.
September 19, 2014: Embraer 505, Lone Star Executive Airport (CXO) in
Conroe, Texas.
Probable cause: The second-in-command's engagement of the emergency parking brake, which decreased the airplane's braking performance.
May 31, 2014: Gulfstream GIV, Laurence G. Hanscom Field (BED) in Bedford,
Massachusetts.
Probable cause: The flight crewmembers' failure to perform the flight control check before takeoff, their attempt to take off with the gust lock system
engaged, and their delayed execution of a rejected takeoff after they became
aware that the controls were locked.
March 16, 2014: Cessna 500 at Zephyrhills Municipal Airport (ZPH) in Florida.
Probable cause: The pilots' inadequate in-flight planning and improper selection
of Runway 36 for landing, which resulted in a significant quartering tailwind during the landing, exceedance of the airplane's braking capability, and a subsequent runway overrun.

Given the frequency of runway overruns,
and the difficulty in accurately predicting
stopping distance on contaminated runways,
how can pilots minimize their risk-short
of ruling out anything but landing on dry
runways?
First, when approaching a non-dry runway, the pilot must be extra vigilant about
meeting stabilized approach criteria, and be
ready for and committed to a go-around if
all parameters are not met. Next, they should
realize that non-dry performance numbers
given in their airplane flight manual or pilot's
operating handbook are estimates only-the
manufacturer will clearly state they are for
advisory purposes and cannot be counted
upon. Given this, if the runway length is
close to the published required runway, little to margin for error likely exists, and the

pilot should consider looking for another,
longer runway. Hoping to meet a manufacturer's landing performance numbers is
never a good strategy, but it's especially risky
on contaminated surfaces.
Finally, after landing out of a well-flown,
stable approach on a conservatively long
runway, the pilot should use immediate and
full stopping aids until at taxi speed. Many
excursions have resulted from a pilot's delaying full brake application until it's too late.
Remember: Braking is not likely to be consistent during the rollout. If good braking is
found right after touchdown, trusting that it
will persist for the length of the runway has
often proven to be trust misplaced. AOPA
NEIL SINGER is a Master CFI with more than

9,500 hours in 15 years of flying.

AOPA Turbine Pilot Magazine - April 2019

Table of Contents for the Digital Edition of AOPA Turbine Pilot Magazine - April 2019